One exercise device which simulates the exercise encountered during the climbing of stationary stairs is described in U.S. Pat. No. 3,970,302, issued to Richard McFee. In this exercise device, moveable steps are provided on an inclined track, with the counterforce being provided hydraulically, in one case by actuation of a hydraulically damped variable pivot lever and in another case by a hydraulic motor. In both of these cases, the steps are moved in opposition or phased mechanically such that when one step is moved downwardly by the weight of an individual, the other step is moved upwardly. In the McFee patent, the mechanical phasing of the steps is accomplished by a wire or chain from one stair to the other over a pulley or hydraulic motor sprocket. The mechanical phasing assures that when one step goes up by a predetermined amount, the other step will come down by this predetermined amount. It should be noted however that should the wire or chain break, the steps are unsupported and an individual can fall off the device. As will be appreciated, mechanical phasing results in a large number of moving parts and mechanical linkages which are noisy, cumbersome and expensive. Moreover, both the pivoted arm embodiment and the hydraulic pump embodiment of the McFee patent are difficult to implement because they do not accommodate the expansion of the hydraulic fluids occasioned by temperature increases associated with use, as energy expended by the user's efforts is absorbed. Also significant backlash accompanies use of these two embodiments which is annoying. Moreover, in the pump embodiment it is extremely difficult to provide a pump which acts symmetrically in both directions. Additionally, neither of the two McFee embodiments allow for compact packaging because the phasing apparatus is bulky and in one embodiment is accomplished by a large number of mechanical parts not conveniently housed in a flat package which would permit compact storage and ready portability.
Additionally, in any conveniently sized pivoted arm embodiment, to adjust the counterforce by 5% for a 100 lb. person corresponding to a change in climbing rate from 60 ft. per minute to 63 ft. per minute, the fulcrum of the pivoted arm is to be changed by less than 1/8 inch, which is virtually impossible to do. This severely limits repeatability of the counterforce setting and the ease with which the counterforce can be varied. Repeatability of the counterforce setting is important because exercise regimens specified by exercise physiologists often progress in intensity from one week to another by increments of only 5% or less.
It will, however, be appreciated that the device described in the above-mentioned patent has advantages over other types of exercise devices such as rowing machines, stationary exercise bicycles, and endless belt walkers.
By way of further background, with respect to exercise bicycles, these devices rely on a pedal driven wheel and either a roller or brakes for providing the counterforce. The problem with these types of exercise devices is the extra amount of effort necessary to start the wheel moving from a dead stop. Moreover in the case of brakes, after the static coefficient of friction has been overcome, the brake pads or strap provide relatively little counterforce. Thus, adjustment of such a device is difficult.
Aside from getting the wheel started, in all of the above-mentioned devices, the amount of counterforce is not readily adjustable and is non-linear. More specifically, the above-mentioned exercise cycles are to a certain extent speed sensitive in that the counterforce applied to the reaction part actuated by the user is speed dependent. For instance in the exercycle, the counterforce lessens substantially as the user exercises since the heating up of the friction pads results in a decreased coefficient of friction during exercise. This is also true for the resilient rim exercycles in which the roller forms a standing wave which makes the exercycle easier to pedal.
By way of further background, perhaps one of the more important problems in terms of home use exercise devices is the noise and vibration associated with these devices. When these devices are utilized in apartments, for instance, the noise and vibration can be so significant that the user is required to forego the use of the exercise device due to the annoyance it causes neighbors. Moreover, if the user prefers to watch television or listen to radio during exercise, the exercise device is sometimes so noisy that it drowns out either the television or the radio. In all of the prior art devices mentioned above, there are a plurality of mechanical parts and mechanical linkages which are inherently noisy. For instance, bike chains, rollers and pivoted levers are amongst those mechanical devices which create considerable noise during operation.